In the process of acquiring oil and/or gas from a well, it is often necessary to stimulate the flow of hydrocarbons via hydraulic fracturing. The term “fracturing” refers to the method of pumping a fluid into a well until the pressure increases to a level that is sufficient to fracture the subterranean geological formations containing the entrapped materials. This process results in cracks and breaks that disrupt the underlying layer to allow the hydrocarbon product to be carried to the well bore at a significantly higher rate. However, unless the pressure is maintained, the newly formed openings close. In order to open a path and maintain it, a propping agent or “proppant” can be injected along with the hydraulic fluid to create the support needed to preserve the opening. As the fissure is formed, the proppants are delivered in a slurry where, upon release of the hydraulic pressure, they form a pack or a prop that serves to hold open the fractures.
Typical fracturing fluids contain around 1-6 pounds of proppant per US gallon of fracturing fluid (ppa), but can be as high as 10 ppa. The most common types of proppants are grains of silica sand (raw or resin-coated) and man-made (engineered) ceramic material.
The proppant that has to be used in a formation depends on many factors. Proppants have to deal with high pressures, temperatures and fluids especially water (fresh and brine), oil and gas. The ideal propping agent is strong, resistant to crushing, resistant to corrosion, has a low density, and is readily available at low cost. The products that best meet these desired traits are silica sand, resin-coated sand (RCS), and ceramic proppants.
Silica sand is the most commonly used proppant as it is much less expensive per pound than RCS and ceramic proppants.
Self-suspending proppants have been developed (US20140060832) to allow the particles to go deeper into the fracture, further increasing the production capabilities. Simplistically, these proppants are sand particles coated with hydratable polymer. When the polymer hydrates it decreases the overall density of the proppant particle and becomes a self-suspending proppant. In turn, the self-suspending proppant is able to flow farther into the fracture without settling out.